The Disappearance of Flow

Abstract

We investigate the disappearance of collective flow in the reaction plane in heavy-ion collisions within a microscopic model (QMD). A systematic study of the impact parameter dependence is performed for the system Ca+Ca. The balance energy strongly increases with impact parameter. Momentum dependent interactions reduce the balance energies for intermediate impact parameters $b\approx 4.5$ fm. Dynamical negative flow is not visible in the laboratory frame but does exist in the contact frame for the heavy system Au+Au. For semi-peripheral collisions of Ca+Ca with $b\approx 6.5$ fm a new two-component flow is discussed. Azimuthal distributions exhibit strong collectiv flow signals, even at the balance energy.

Comments: 19 pages, 7 eps-figures, uses psfig.sty; complete postscript file available at ftp://th.physik.uni-frankfurt.de/pub/bass/GSI-preprint_95-11.ps.Z